1. Field of the Invention
The invention relates in general to detecting framing and decoding coded electric signals and more particularly to detecting, framing and decoding coded electric signals derived from scanning a Universal Product Code (UPC) label with an opto-electric scanner which produces electric signals which are an analog of the optical bar coded label.
2. Description of the Prior Art
The UPC coded label and similar coded labels have dimensional optical characteristics which define with precision the coded information in the label in a form suitable for use in a data processing system. All that is required in order to decode the information is knowledge of the dimensional characteristics and a known algorithm which defines calculations which will yield the information in usable form. For example, a UPC label is provided with two guard bars (areas of lower reflectivity separated from each other and from adjacent areas of similar reflectivity by spaces, areas of higher reflectivity). The dimensions of the spaces and guard bars are selected as to differ sufficiently from the bars and spaces defining the coded information so as to indicate the beginning of the coded information. The coded information is contained on a character basis in two bars and two spaces occupying a fixed space. Twelve characters divided into two groups of six separated by a unique separator character comprise a label.
An absolute measurement of the bar and space widths when a hand-driven scanner is used is impossible since the velocity of the scanner is unknown and subject to wide variation. The code, however, may be located, framed and decoded by calculating selected ratios. These calculations, however, require arithmetic units which, when provided for this function only, are economically burdensome.